Tag Archives: Physics

Building a better battery

A new battery technology provides double the energy storage at lower cost than the batteries that are used in handheld electronics, electric vehicles, aerospace and defence.

The batteries used in these applications are typically based on lithium and a metal oxide, such as cobalt, manganese or nickel. Researchers from the University of Cambridge have developed a composite of sulphur and nanostructured carbon, for use as a battery cathode with much higher energy storage at much lower cost than conventional materials.

 

The cathode, or positive electrode, is one of three functional components of a battery, along with the anode (negative electrode) and electrolyte. The raw cathode materials are the single largest material cost in battery production, representing between 35 and 40 per cent of total costs.

The global lithium-ion battery market is expected to expand to $54 billion by 2020, up from $11.8 billion in 2010, driven primarily by demand from the consumer electronics and electric vehicle sectors.

“Using sulphur instead of the materials currently used in lithium-ion batteries could substantially reduce production costs, as sulphur is a fraction of the cost of other materials,” says Dr Can Zhang of the Department of Engineering, one of the developers of the material. “Additionally, compared with conventional lithium-ion batteries, the carbon-sulphur electrodes achieve double the energy density per unit of weight.”

The carbon-sulphur electrodes are produced by growing a “forest” of high-quality carbon nanotubes (CNTs) on a layer of metal foam. The CNT forest provides excellent electrical conductivity, and acts as a three-dimensional scaffold into which the sulphur is injected in order to form the cathode.

The sulphur is trapped within the scaffold in the form of small particles which store electrons. The pore structure of the metal foam, combined with the dense vertical packing of CNTs, provides a labyrinth with a large surface area for the retention of electrode material.

Despite their higher density and lower costs, the commercial development of lithium-sulphur batteries has been largely plagued by short cycle life, typically below 80 charge-discharge cycles. In comparison, a conventional lithium-ion battery will usually achieve 500 charge-discharge cycles. The CNT-sulphur composite significantly enhances the cycle performance of lithium-sulphur batteries, retaining 80% capacity after over 250 full charge-discharge cycles.

The work is the result of a collaboration between the groups of Professor John Robertson of the Department of Engineering and Dr Vasant Kumar of the Department of Materials Science and Metallurgy.

Dr Zhang, a postdoctoral researcher in Professor Robertson’s group, has formed CamBattery to commercialise the technology, along with PhD students Bingan Chen, Kai Xi and Wentao He. The company won Technology Start-up of the Year at the 2012 Cambridge University Entrepreneurs competition.

Over the next two years, the team intends to build the first roll-to-roll machine to continuously produce the cathode material, and sell the product to major battery manufacturers. While the number of charge-discharge cycles achieved by lithium-sulphur batteries is not yet high enough for CamBattery to enter the consumer electronics market, applications in aerospace and defence are strong possibilities. “For aerospace and defence applications, energy storage takes precedence over life cycle,” says Dr Zhang. “However, we will continue working at getting the number of life cycles high enough for consumer electronics and electric vehicles.”

The Cambridge University Entrepreneurs (CUE) Business Creation Competition is the UK’s biggest student business plan competition. Since its creation in 2000, the competition has had more than 1,000 entries and awarded £500,000 in prize money to students and staff. Companies from the competition have gone on to raise close to £70 million in further funding.

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Quantum Refrigerator Offers Extreme Cooling and Convenience

NIST's prototype solid-state refrigerator uses quantum physics in the square chip mounted on the green circuit board to cool the much larger copper platform (in the middle of the photo) below standard cryogenic temperatures. Other objects can also be attached to the platform for cooling. Credit: Schmidt/NIST

NIST’s prototype solid-state refrigerator uses quantum physics in the square chip mounted on the green circuit board to cool the much larger copper platform (in the middle of the photo) below standard cryogenic temperatures. Other objects can also be attached to the platform for cooling.
Credit: Schmidt/NIST

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a solid-state refrigerator that uses quantum physics in micro- and nanostructures to cool a much larger object to extremely low temperatures.

What’s more, the prototype NIST refrigerator, which measures a few inches in outer dimensions, enables researchers to place any suitable object in the cooling zone and later remove and replace it, similar to an all-purpose kitchen refrigerator. The cooling power is the equivalent of a window-mounted air conditioner cooling a building the size of the Lincoln Memorial in Washington, D.C.

 

“It’s one of the most flabbergasting results I’ve seen,” project leader Joel Ullom says. “We used quantum mechanics in a nanostructure to cool a block of copper. The copper is about a million times heavier than the refrigerating elements. This is a rare example of a nano- or microelectromechanical machine that can manipulate the macroscopic world.”

The technology may offer a compact, convenient means of chilling advanced sensors below standard cryogenic temperatures—300 milliKelvin (mK), typically achieved by use of liquid helium—to enhance their performance in quantum information systems, telescope cameras, and searches for mysterious dark matter and dark energy.

As described in Applied Physics Letters,* the NIST refrigerator’s cooling elements, consisting of 48 tiny sandwiches of specific materials, chilled a plate of copper, 2.5 centimeters on a side and 3 millimeters thick, from 290 mK to 256 mK. The cooling process took about 18 hours. NIST researchers expect that minor improvements will enable faster and further cooling to about 100 mK.

The cooling elements are sandwiches of a normal metal, a 1-nanometer-thick insulating layer, and a superconducting metal. When a voltage is applied, the hottest electrons “tunnel” from the normal metal through the insulator to the superconductor. The temperature in the normal metal drops dramatically and drains electronic and vibrational energy from the object being cooled.

NIST researchers previously demonstrated this basic cooling method** but are now able to cool larger objects that can be easily attached and removed. Researchers developed a micromachining process to attach the cooling elements to the copper plate, which is designed to be a stage on which other objects can be attached and cooled. Additional advances include better thermal isolation of the stage, which is suspended by strong, cold-tolerant cords.

Cooling to temperatures below 300 mK currently requires complex, large and costly apparatus. NIST researchers want to build simple, compact alternatives to make it easier to cool NIST’s advanced sensors. Researchers plan to boost the cooling power of the prototype refrigerator by adding more and higher-efficiency superconducting junctions and building a more rigid support structure.

Students developing next-generation e-Books platform

The electronic book industry is booming; nearly a quarter of Americans are reading e-books, and sales of e-book readers and tablets — including Amazon’s Kindle, Barnes & Noble’s Nook, and Apple’s iPad — continue to grow. But the increase in e-book sales is accompanied by a growing chorus of complaints that the current e-book publishing system is fundamentally broken.

“There are a lot of problems in publishing. It’s very centralized: the Kindle is a locked system, and iBooks is a locked system. It’s frustrating for e-book developers,” said Jake Hartnell, a first-year MIMS student at the School of Information.

 

Other criticisms focus on digital rights management, the restriction of having books locked inside a specific device, and questions about long-term sustainability. “People who buy an e-book have no assurance that today’s book will be readable in the future,” explained Lisa Jervis, another first-year MIMS student.

Now a group of students from the School of Information is developing a next-generation platform for electronic books that promises to resolve these challenges and more.

The students are enrolled in the course Info 290. The Future of E-Books; the class includes ten graduate students from education, cognitive science, and the School of Information, including Hartnell and Jervis. The class is working together this semester to design and develop an open-source, platform-independent framework for publishing e-books, along with tools for authors, editors, and publishers. Their framework is based on HTML5, which allows it to support a wide range of multimedia content, as well as the possibility of customizable content, interactivity, and social tools. HTML5 allows books to be read on a variety of devices, including in a standard web browser.

Although the framework is web-based, the design uses HTML5 storage to save the book permanently in the browser’s or device’s cache, making books fully accessible even without Internet connectivity. In a nod to economic realities, the framework includes tools to allow publishers to charge for content, or to automatically delete the book from the cache after a preset expiration date. Responsive frameworks will let the same content be optimized for display on a variety of devices, from phones to tablets to desktop web browsers.

Initially, the team is focusing on the reader’s experience. The students are taking the best features of the ePub standard and adding it to HTML5. “We want to make reading on the web a great experience,” said Hartnell.

Hartnell is not just an information graduate student; he’s also a science fiction author. As an author, he’s especially excited by the creative possibilities the new framework offers. “In most e-books formats, your options for controlling layout and styling and design are very limited,” he explained. “As a writer, I’m looking forward to using the stuff we’re building; it allows me to post my book online in a beautiful fashion and share it. I think people still have the desire to make beautiful-looking things.”

The second phase of development will focus on tools for authors, editors, and publishers. Lisa Jervis is particularly focused on supporting authors and editors. She was the founding editor and publisher of Bitch, author of Cook Food, and the co-editor of Young Wives’ Tales and Bitchfest; her writing has appeared in Bitch, Ms., the San Francisco Chronicle, Utne, Mother Jones, theWomen’s Review of Books, Bust, Salon, and more.

“In my fifteen years of work as an editor, I’ve developed a deep understanding of how content is produced and honed,” said Jervis. “I want to use that experience to design a tool that incorporates editorial best practices, in a way that encourages the production of high-quality content.”

Jervis is also excited about building editorial workflows and tools to support collaborative authoring. “There are lots of new models for collaborative content creation, but none of them are well suited for the long form of books,” she explained. “A book requires a different editorial control model than Wikipedia.”

The students expect that this semester’s work will just be the beginning. The new platform will be open-source and modular, to encourage other developers to add new tools and features.

One possibility is interactive books — textbooks could include quizzes and interactive tutorials. A developer could also create customizable content — readers of a textbook or instruction manual could choose examples targeted to their specific industry or application. The platform could also support social tools like open annotation — imagine sharing your comments or notes with friends who are reading the same book.

“The possibilities are really endless,” said Hartnell.

Blueprint for an artificial brain

 

 

A nanocomponent that is capable of learning: The Bielefeld memristor built into a chip here is 600 times thinner than a human hair.

Scientists have long been dreaming about building a computer that would work like a brain. This is because a brain is far more energy-saving than a computer, it can learn by itself, and it doesn’t need any programming. Dr. Andy Thomas from Bielefeld University’s Faculty of Physics is experimenting with memristors – electronic microcomponents that imitate natural nerves. Thomas and his colleagues proved that they could do this a year ago. They constructed a memristor that is capable of learning. Andy Thomas is now using his memristors as key components in a blueprint for an artificial brain.

 

He will be presenting his results at the beginning of March in the print edition of the prestigious Journal of Physics published by the Institute of Physics in London.

Memristors are made of fine nanolayers and can be used to connect electric circuits. For several years now, the memristor has been considered to be the electronic equivalent of the synapse. Synapses are, so to speak, the bridges across which nerve cells (neurons) contact each other. Their connections increase in strength the more often they are used. Usually, one nerve cell is connected to other nerve cells across thousands of synapses.

Like synapses, memristors learn from earlier impulses. In their case, these are electrical impulses that (as yet) do not come from nerve cells but from the electric circuits to which they are connected. The amount of current a memristor allows to pass depends on how strong the current was that flowed through it in the past and how long it was exposed to it.

Andy Thomas explains that because of their similarity to synapses, memristors are particularly suitable for building an artificial brain – a new generation of computers. ‘They allow us to construct extremely energy-efficient and robust processors that are able to learn by themselves.’ Based on his own experiments and research findings from biology and physics, his article is the first to summarize which principles taken from nature need to be transferred to technological systems if such a neuromorphic (nerve like) computer is to function. Such principles are that memristors, just like synapses, have to ‘note’ earlier impulses, and that neurons react to an impulse only when it passes a certain threshold.

Thanks to these properties, synapses can be used to reconstruct the brain process responsible for learning, says Andy Thomas. He takes the classic psychological experiment with Pavlov’s dog as an example. The experiment shows how you can link the natural reaction to a stimulus that elicits a reflex response with what is initially a neutral stimulus – this is how learning takes place. If the dog sees food, it reacts by salivating. If the dog hears a bell ring every time it sees food, this neutral stimulus will become linked to the stimulus eliciting a reflex response. As a result, the dog will also salivate when it hears only the bell ringing and no food is in sight. The reason for this is that the nerve cells in the brain that transport the stimulus eliciting a reflex response have strong synaptic links with the nerve cells that trigger the reaction.

If the neutral bell-ringing stimulus is introduced at the same time as the food stimulus, the dog will learn. The control mechanism in the brain now assumes that the nerve cells transporting the neutral stimulus (bell ringing) are also responsible for the reaction – the link between the actually ‘neutral’ nerve cell and the ‘salivation’ nerve cell also becomes stronger. This link can be trained by repeatedly bringing together the stimulus eliciting a reflex response and the neutral stimulus. ‘You can also construct such a circuit with memristors – this is a first step towards a neuromorphic processor,’ says Andy Thomas.

‘This is all possible because a memristor can store information more precisely than the bits on which previous computer processors have been based,’ says Thomas. Both a memristor and a bit work with electrical impulses. However, a bit does not allow any fine adjustment – it can only work with ‘on’ and ‘off’. In contrast, a memristor can raise or lower its resistance continuously. ‘This is how memristors deliver a basis for the gradual learning and forgetting of an artificial brain,’ explains Thomas.

 

 

Surviving Radiation in Space

Astrowright

For those who are interested in the reality of radiation exposure on Earth, in space, on the Moon, and what this exposure means for our prospects of manned exploration of the Solar System, read on!

The Myths and Truths of Death by Space Radiation

There are persistent groves of misinformation taking root about the lethality of radiation doses for astronauts, particularly for those who are bound for the Moon and/or Near-Earth-Objects, (such as asteroids for research or mining).

Unfortunately, these claims have been given the capacity for widespread proliferation in the fertile cyber-soil of the Internet, and worse, they usually sprout symbiotically with claims that the Moon landings were hoaxed, e.g.:

“We could never have landed on the Moon because the astronauts could never have survived the radiation from cosmic sources/the Van Allen Belts/solar wind.  Therefore, at a sound stage in the Nevada desert…”

Well, since most of these authors…

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